Methods of plant diseases control

The main objective of plant pathology is the economic control of plant disease. However,
the term control evokes the notion of finality or completeness, which is not true in nature.
Whereas the word “Management” conveys the concept of a continuous process and management
is based on the principle of maintaining the damage or less below an “economic injury level”.
Methods of plant diseases control involves following practices:
1. Cultural methods
2. Physical methods
3. Regulatory methods
4. Biological methods
5. Host resistance development
6. Chemical methods

Insecticide, Fungicide, Herbicide, etc

Suppression

Resistance Selection, Breeding, Biotechnology

Monitoring Mycoparasite, hyperparasites, antagonists

Quarantine, Certification
Legal check

Avoidance Pruning, Mulching, Barriers, Weeding

Prevention Site & Plant Selection, Sanitation, Rotation

I. CULTURAL CONTROL

The term cultural control describes the activities of humans aimed at controlling disease
through the cultural manipulation of plants. The success of cultural control practices ultimately
depends on understanding the biology of the pathogen and the response of the host to infection.
Such knowledge facilitates management decisions which 'attack' parasites at vulnerable stages of
their life cycles. It may be difficult to assess their effectiveness because the farming operations
are often performed well in advance of expected pathogen attacks.
Cultural practices involves all the activities carried out on the farm before, during and
after planting of crops. They are grouped into: pre-planting, planting and post planting operation.
So pre planting operations can include choice of site, then clearing of land, Stumping, Ploughing,
Harrowing and Ridging. So, these are some of the practices that are normally done before
planting of the crop. Similarly, planting operations include Planting, Transplanting and Nursery
practices. So these are operations that are done during the plantation of the crop and the post
planting operations include thinning, supplying, mulching, manuring, watering, weeding, Pest

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and disease management, harvesting, processing and storage. So, the post planting operation is
also significant in reducing the disease inoculum.
Pre planting operations:
1.Crop rotation
Crop rotation is essentially a preventive measure and has its effect mainly on the
succeeding crop. Crop rotation is the oldest and cheapest method adopted in agriculture for
eradication of certain types of pathogens from infested soil. Continuous cropping or
monoculturing provides opportunity for perpetuation of pathogenic organisms in the soil when
the same crop is raised year after year in the same field. Crop rotation with sugarcane or paddy is
effective in the control of ‘Panama wilt’ of banana (Fusarium oxysporum f.sp. cubense) and crop
rotation with paddy or green manures is effective in the control of red rot of sugarcane
(Colletotrichum falcatum). Rotation of cereal crops like pearlmillet, finger millet or fox-tail
millet is recommended for the control of Macrophomina root rot of pulse crops.
2. Fallowing
Fallowing starves the pathogen and helps in reduction of the inoculum by elimination of
the host. Diseases like Macrophomina root rot on different crop plants is controlled by following
this method. Flood fallowing is to a depth of 0.6 to 1.5 m for 4 to 6 months markedly reduced the
Panama wilt pathogen Fusarium oxysporum f.sp.cubense inoculum in banana. Flooding the soil
strewn with debris infected by Xanthomonas axonopodis pv. malvacearum for 4 days reduced
the inoculum level and thus the incidence of disease was only 2.1% as against 69.5% in
unflooded fields. Wet fallowing reduces saprophytic survival of Alternaria solani on crop debris.
3. Application of organic manures
Addition of organic manures like farm yard manure or green manures or oil cakes to the
soil increases the antagonistic microorganisms in the soil. Build up of antagonistic
microorganisms reduces the population of soil borne plant pathogens and the diseases caused by
them. Application of farm yard manure at the rate of 12.5 tonnes/ha reduced the incidence of
Macrophomina root rot of cotton. In the control of sesame root rot (Macrophomina phaseolina)
application of neem cake at the rate of 150 kg/ha is recommended.
4. Soil amendment
It has been proved that the organic amendments rich in carbon and deficient in nitrogen
control the take-all disease (Ophiobolus graminis) of wheat. There is considerable liberation of
CO2 by soil saprophytes which suppresses the pathogenic activity of this fungus .In the process
of survival also, low nitrogen content in the soil reduces the longevity of the fungus.
Phytophthora root rot of avocado is controlled by amending the soils with alfalfa meal- a
material of low C/N ratio. The other diseases are pea root rot Aphanomyces euteichus when
cruciferous plant residues were incorporated into the soil.
5 .Summer ploughing
Deep ploughing during summer periods buries the inocula of fungi of soil borne nature.
Fungal propagules, sclerotia and different types of spores conidia on plant refuses die when
exposed to sunlight due to the higher temperature prevailing during the summer. Further infected
self sown plants, volunteer hosts plants, weed hosts, regrowths from the plant roots, alternate

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hosts and alternative hosts are also destroyed. Here, the spread of the disease is avoided.
Groundnut blight (Corticium rolfsii) is controlled by ploughing the soil to a depth of 20 cm. The
inverted plough sole soil buries the sclerotia of the fungi, Claviceps, Sclerotium and Sclerotinia
in association with plant or alone.
7. Leveling of the field and provision of drainage facilities
Water stagnation in different patches of field favours the fungi like Pythium,
Phytophthora, Rhizoctonia solani, etc., for which proper leveling of the field before sowing or
planting is very essential.
7. Burning of stubbles and crop residues
Burning of plant wastes, crop residues, stubbles, etc., in the areas selected for raising
nurseries for vegetable crops, tobacco, chillies and forest trees etc. heats the soil and kills the
inoculum of the pathogens present in the top layer of the soil. When nurseries are raised in these
areas incidence of damping off disease is highly reduced. Otherwise, debris in the field helps the
perpetuation of the pathogen and the disease. Burning of rice crop residues avoid carryover of
sheath blight (Rhizoctonia solani); stem rot (Sclerotium oryzae) of rice and bacterial blight of
cotton.
During Crop growing seasons
1. Adjustment of sowing time
In many diseases the incidence is more severe when the susceptible stage of the plant
growth and favourable conditions for the pathogens coincides. While choosing the time of
sowing it should be taken into consideration that susceptible stage of the crop growth and soil
conditions and other environments favourable for maximum activity of the pathogen does not
fall at the same time. Avoiding cool and cloudy days for planting will help to reduce red rot of
sugarcane. Late sowing of winter wheat and barley is considered to be the most effective
measures in reducing take all disease of wheat. Rapeseed sown in mid to late August is more
liable to attack by leaf spot (Alternaria brassicae) than late-sown crops. Stem rust of wheat
damages the late sown crop more than the early sown crop. Because, time of onset of disease and
ear formation coincides.
2. Selection of seeds and seed materials
Seeds and seed materials carry many fungi, bacteria, viruses and phytoplasmas and may
introduce these pathogens into the field, i.e., seeds and seed materials form the primary source of
infection. Seed and seed materials like cuttings, tubers, grafts, setts etc., should be well matured,
disease free, uninjured and have a high germinating capacity. The absence of an initial inoculum
in seeds is definitely helpful in delaying or suppressing the incidence of the disease. It is a
preventive method.
The diseases like foot rot, brown spot, short smut of sorghum, loose smut of wheat,
bacterial blight of rice, bacterial blight of cotton, leaf crinkle of blackgram etc., are transmitted
through seeds.

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3. Seed rate
Use of higher seed rate in the nursery creates favourable microclimate for the pathogens
causing damping-off in vegetables, tobacco, chillies and forest nurseries. Hence, use of optimum
seed rate should be adhered in such crops.
4. Depth of sowing
Depth of sowing greatly influences seed transmission of smuts. Shallow planting in wet
soils protects wheat plants from Urocystis tritici (flag smut) of wheat. Deep planting may cause
delay in the emergence of seedlings, which may be vulnerable to pre-emergence damping off.
Early emergence results in early lignification of tissues which become resistant to attack of soil-
borne pathogens.
5. Spacing
Closer spacing invariably alters the microclimate underneath the canopy of the crop
which may provide favourable environment for development of diseases. Closer spacing favours
many air borne diseases because of high humidity in the crop canopy. Early and late blight of
groundnut and blister blight of tea are more in dense canopy. Early spread of black rot of
cabbage takes place in closer spacing. Crowded stands may reduce some systemic diseases.
Cotton wilt caused by Verticillium albo-atrum will be less in closely planted crop if the fungal
inoculum is less in the soil.
6. Method of sowing/planting
In places where water accumulation is a problem to the crop growth sowing of seeds on
the sides or ridges is found effective in reducing the incidence of Sclerotium rolfsii on groundnut
and vegetable crops and Sclerotinia sclerotiorum and Rhizoctonia solani on vegetable crops and
Phytophthora blight of pigeonpea.
7. Mixed cropping
Mixed cropping materially helps in checking certain diseases. Blight of pulse crop
(Phyllosticta phaseolina ) has been successfully overcome by growing pulses as a mixed crop
with cereals like sorghum and pearlmillet.
8. Intercropping
Intercropping is also a device in the control of some soil borne diseases. Intercrops
should be properly chosen so that they should not have any common pathogen for e.g.,
Macrophomina phaseolina has got wide host range and hence common host should not be grown
as intercrops. Intercropping with moth bean (Phaseolus aconitifolius) in a cotton field reduced
the root rot (M.phaseolina) incidence.
9. Decoy crop and trap crop
Decoy crops (hostile crops) are non-host crops sown with the purpose of making soil-
borne pathogens waste their infection potential. This is effected by activating dormant
propagules of fungi, seeds of parasitic plants, etc. in absence of the host. A list of pathogens that
can be decoyed is given in table.

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 Trap crops are host crops of the pathogen, sown to attract pathogens but destined to be
harvested or destroyed before they complete their life cycle. Fodder sorghum can be raised as a
trap crop to reduce downy mildew of sorghum.
Post planting operations:
1. Mulching
Mulching or covering of top soil with organic residues often helps in reducing plant
diseases. Mulches of non-host origin should be used in the field. These mulches are known to
release inhibitory substances in the underlying soil and also promote development of parasites
and predators of nematodes. Reflective surfaces (mulches) laid on the soil around the crop plant,
have been found to be highly effective in controlling aphid vectors.
2. Irrigation water management
Irrigation to the crop in the field is to wet the soil to the extent that roots easily get water
and nutrients. If excess water is added to soil, it may directly affect activity of pathogens and/or
it may affect disease incidence through the effect on the host. Scab attack on potato tubers is
prevented by maintaining soil moisture near field capacity during tuber formation. Bacterial flora
antagonistic to Streptomyces scabies increases under high moisture conditions. When excess
irrigation is made the juvenile stage of plants is lengthened making it susceptible to attack of
fungi like Pythium. Supply of frequent but low quantity of irrigation water is, therefore,
recommended for reducing chances of damping off in nurseries.
3. Roguing
Roguing consists of completely removing or uprooting the diseased plants to prevent
further spread of the disease. This method is widely adopted in the control of virus diseases
spread by insects (cassava mosaic, yellow mosaic of blackgram and greengram, citrus tristeza,
katte disease of cardamom, bunchy top of banana) and basal stem rot of coconut, green ear of
pearlmillet and broomrape (Orobanche) in tobacco. The whip smut of sugarcane (Ustilago
scitaminea) in the canal areas of Bombay in Co.475 variety has been greatly checked by roguing
carried out over wide areas and long period.
4. Management of plant nutrients
The plant nutrients in general when applied in excess may increase or reduce the
resistance in plants to diseases. Increased application of nitrogenous fertilizers increases the
incidence of many diseases. Crops fed with heavy doses of nitrogenous was fertilizers grow
robust with foliage and succulent tissue but become highly susceptible to the attack of diseases
like rust powdery mildew, blast, tobacco mosaic and some bacterial diseases .In the case of blast
of rice optimum dose of nitrogenous fertilizers are recommended and it is applied in 3 split doses
viz. 50% as based at transplanting, 25% at tillering and 25% at panicle initiation stage. Late
application of nitrogenous fertilizers increases wheat leaf blotch ( Septoria nodorum) and
powdery mildew ( Erysiphe graminis tritici).

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6. Avoiding injury
Injury of plant parts should be avoided in order to check the entry of pathogens. Clipping
of tips of tall rice seedlings favours the entry of bacterial blight pathogen and incidence of the
disease. Hence clipping should be avoided at the time of transplanting of rice. While harvesting
the pods in groundnut, fruits in tree crops and vegetable crops injuries to the fruits pave the way
for the pathogen and causing pod/fruit rot. It also reduces the storage life of fruits and vegetables.
Hence much care should be given to avoid wounds during the harvest time.
7. Time of harvesting
Time of harvesting affects the cleanliness of the seeds. Delayed harvesting of grain crops
in temperate climatic conditions enables the pathogen more time to contaminate the seeds. The
best example is grain mould of sorghum where contamination by species of Fusarium,
Curvularia, Alternaria, Aspergillus, Phoma is seen. Potato tubers harvested when the tops are
green get easily contaminated by the late blight pathogen present on the leaves. Removal of tops
and making them to dry before digging the tubers kills the sporangia and avoids contamination
of tubers harvested later.
8. Avoiding ratooning
Ratooning is a general practice in sugarcane when the incidence of grassy shoot disease
and red rot are very high. Hence ratooning should be avoided.
II. PHYSICAL METHODS
Introduction
Physical methods for disease control as alternative to fungicides for
the management for seed and soil-borne pathogens, and for integration in
disease management programs. They usually do not leave residues or
pollute the environment.

The Principle
The scientific principle involved in heat therapy is that the pathogen
present in seed material is selectively inactivated or eliminated at
temperatures that are non-lethal to the tissues. The exact mechanism by
which heat inactivates the pathogen is not fully understood. It is universally
accepted that heat cause inactivation and immobilization of the pathogen.
There are two of thoughts regarding inactivation of pathogen (viruses) by
heat.May be the chances that heat leads loosening of bonds both in nucleic
acid and the protein components of the virus. In the nucleic acid, when the
bonds are disrupted the linear arrangement of nucleotides is disrupted and
thus the virus looses infectivity. In proteins, the bonds holding the chains of
amino acids may be destroyed. Disruption of bonds causes denaturing of
protein molecules which become less soluble in water and finally leads to
coagulation. The rate at which the pathogen is inactivated is determinate by
temperature and the duration of treatment.

Methods for managing Seed-borne Pathogens

Some of the seed treating procedure do not involve the use of
fungicides, the physical agents like hot water or hot air or steam is used to
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eliminate the seed-borne infection. These methods are successfully used in
controlling certain internally seed-borne diseases like loose smut of wheat
and systemically infected diseases caused by bacterial, virus,viral and
phytoplasma. Following physical methods are employed for reduction and/or
elimination of primary inoculums that may be present in seed or planting
material:

1) Hot Water Treatment: Hot water treatment is widely used for the control of seed-borne
pathogens, especially bacteria and viruses. A list some important seed-borne diseases, which can
be controlled by hot water treatment is given below:

Crop Disease Causal Organism Treatment

Brassica Black rot X. campestris pv. campestris 50ºC for 20 or 30 min
spp.
Cluster Blight X. campestris pv. 50ºC for 10 min
bean cyamopsidis
Pearl millet Downy Sclerosporagraminicola 55ºC for 10 min
mildew
Sugarcane Red rot Colletotrichum falcatum 54ºC for 8 hr
Sugarcane Mosaic Virus (Potato Virus Y 20 min treatment for
group) 3successive days at 52ºC
Rice Udbatta Ephelisoryzae 54ºC for 10 min
Rice White tip Aphelenchoidesbesseyi 51-53ºC for 15 min

2) Hot Air Treatment: Hot air treatment is less injurious to seed and easy to
operate but also less effective than hot water treatment. It has been used
against several diseases of sugarcane. For example, complete control ofred
rot in varieties Co 527, CoS 510, Bo 3 and Bo 32 by hot air treatment of 54ºC
for 8 hours. Hot air treatment at 54ºC for 8 hours effectively eliminates
RSDpathogen without impairing the germination of buds.
3) Solar Heat Treatment: The treatment has been devised in India to eliminate the pathogen of
loose smut of wheat. Previously the hot water treatment was followed to eliminate loose smut.
As the thermal death point of the fungus and the embryo are very close, extensive care should be
taken to avoid killing of the embryo. Luthra in 1953, devised a method to eliminate the deep
seated infection of Ustilago nuda. The method is popularly known as solar heat or solar energy
treatment.
Luthra’s solar energy treatment: The seeds are soaked in cold water for 4 hours in the
forenoon ona bright summer day followed by spreading and drying the seeds in hot sun for four
hours in the afternoon.

Methods for managing Seed-borne Pathogens

Soil harbours a large number of plant pathogens and the primary
sources ofmany plant pathogens happens to be in soil where dead organic
matter supports active or dormant stages of pathogens. Soil treatment is
largely curative in nature as it mainly aims at killing the pathogens in soil
and making the soil ‘safe’ for the growth of the plant. Some of the commonly
followed physical methods for soil-borne pathogens are:

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1) Soil Solarization: Soil solarization is conduction of heat by entrapment of solar irradiation
through the greenhouse effect. Very thin (25-50 µm) transparent polyethylene (PE) mulch is
commonly used to trap solar heat because it is permeable to the short-wavelength solar radiation,
but does not transmit longer-wavelength radiation (heat) from the ground back into the
atmosphere. Solar radiation with short wavelengths (about 120 - 400 nanometers) carries higher
amounts of energy than does radiation with longer wavelengths (infrared radiation). The
transparent plastic tarp used in solarization transmits ultraviolet (UV) and visible light but not
infrared radiation (IR) known as photoselective PE plastic. As the short-wavelength solar
radiation passes through the plastic layer, it loses energy; the wavelengths increase in length and
the radiation essentially becomes infrared radiation that generate heat. This heat is trapped
beneath the plastic where it warms the soil.
Soil solarization with transparent polyethylene sheet mulch (25μm) for 40 days is
effective for the control of collar and root rot of strawberry caused by Sclerotium rolfsii, Fungal
diseases such as damping-off, root rots, stem rots, fruit rots, wilts and blights caused by Pythium
spp., Phytophthora spp., Fusarium spp., S. rolfsii, R. solani, Sclerotiniasclerotoirum, T. basicola
and Verticillium spp. have been successfully managed by soil Solarization.
Nematode diseases such as Ditylenchus dipsci, Globoderarostochiensis, Heteroderaspp.,
and Meloidogyne spp. have been successfully managed by soil solarization.
Bacterial canker of tomato (Clavibactermichiganensissubsp. michiganensis) is
successfullymanaged by Soil solarization for 1-2 months.

2) Steam Sterilization: Steam is passed through perforated pipes at a depth of

15 cm to sterilize the upper layers of soil. It is mostly practiced under glass
house and green house conditions.

3) Hot Air Sterilization: Hot air is also passed through pipelines to sterilize the
soil in the nursery areas.

4) Hot Water Treatment:It is mainly done in pot culture studies to kill the fungi and
nematodes. The pots containing soil areimmersed in boiling water at 980C for 5 minutes or
drenching boiling water @ 20 liters/m2.

5) Burning: Burning helps in destroying inoculum crop debris or pasture

grasses which can periodically be freed from inoculum before they make new
growth. It has also been realized that the increasing success of non-tillage in
some crops and the resultant problems of debris management can make
burning an attractive and effective proposition.

6) Flooding: Flooding fields and orchards to reduce or eliminate soil-borne

inoculum of plant pathogens is an ancient practice. Flooding has been
recognized to be one of the key factors for the low incidence of soil-borne
disease.

Physical Methods for managing post-harvest losses

1) Refrigeration: Low temperature at or slightly above the freezing point

checks the growth and activities of all such pathogens that cause a variety of
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post harvest diseases of vegetables andfruits. Therefore, most perishable
fruits be transported and stored in refrigerated vehicles and stores.

2) Radiation: Electromagnetic radiations such as ultraviolet (UV) light, X-rays and Y-rays, as
particulate radiations can be used to management of post-harvest diseases of horticultural crops.

III) REGULATORY METHODS – PLANT QUARANTINE AND INSPECTION

Plant Quarantine: The term ‘Quarantine’ has been derived from Latin word ‘Quarantum’
means simply forty i.e., 40 days period. This was more commonly referred to the period of
detention for ships arriving from countries subject to epidemic diseases such as the Bubonic
plague, cholera and yellow fever. The crew and the passengers used to be compelled to remain
isolated on board for sufficient period to permit the diseases to develop and be detected. The
purpose of the health authorities was to establish adequate detention period. Later on, the term
‘Quarantine’ came to be only used for the detention and the practices connected with it. The term
got associated from the human disease field to the animal disease field and later on adopted to
cover protective methods for the exclusion of pests and diseases of agricultural and horticultural
crops.
‘Plant Quarantine’ refers to the holding of plants in isolation until they are believed to be
healthy. Now, broader meaning of the plant quarantine covers all aspects of the regulation of the
movement of living plants, living plant parts/plant products between politically defined
territories or ecologically distinct parts of them. Intermediate quarantine and post entry
quarantine are used respectively to denote the detention of plants in isolation for inspection
during or after arrival at their final destination.

History: The first plant quarantine law was promulgated in Rollen, France in 1860 to suppress
and prevent the spread of common barberry, the alternate host for wheat stem rust. Among other
countries, the first few to establish plant quarantine services were Germany, France, Australia
and the U.S.A. In India, legislative measures against crop pests and diseases was initiated under
the Destructive Insects and pests Act of 1914 (DIP act) and it was passed by Governor General
of India on 3 rd February, 1914. Under this Act, rules governing the import and movement of
plants and plant materials, insects and fungi are framed.

The Act provides:

 It authorizes the Central Government to prohibit or regulate the import into India or any
part there of any specific place therein, of any article of class of articles.

 It authorizes the State Governments to make rules for the detention, inspection,
disinfection or destruction of any insect or class of insects or of any article or class of
articles, in respect of which the Central Government have issued notifications. It also
authorizes the State governments for regulating the powers and duties of the officers
whom it may appoint on this behalf.

Importance of Plant Quarantine: The adoption Quarantine Regulations and acts by different
countries of the world has arisen out of fact that extensive damages often sudden in nature, have

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been caused not by indigenous organisms but by exotic ones which have been cause not by
indigenous organisms but by exotic ones which have been introduced along with plants, plant
parts or seeds in the normal channel or trade or individual transit.

Introduction of new pathogen: Often a new pest, disease or weed has accidentally entered a
country where it did not exist before and has multiplied, spread and caused enormous damage to
the crops of that country.
Table: Diseases believed to have been introduced into India from foreign countries, some
examples are as follows:
S. Disease Country Year
No.
1 Coffee rust (Hemileia vastatrix ) Sri Lanka 1879
2 Late blight of potato (Phytophthora infestans) England 1883
3 Rust of chrysanthemum (Puccinia carthami) Japan / Europe 1904
4 Flag smut of wheat Australia 1906
5 Downy mildew of grapes (Plasmopara viticola) Europe 1910
6 Downy mildew of maize (Scleropora phillipinensis) Java 1912
7 Downy mildew of cucurbits (Pseudoperonospora Srilanka 1918
cubensis)
8 Black rot of crucifers (Xanthomonas campestris) Java 1929
9 Foot rot of rice (Fusarium moniliforme) South East Asia 1930
10 Leaf spot of sorghum ( South Africa 1934
11 Powdery mildew of rubber (Oidium heveae) Malaya 1938
12 Black shank of tobacco Holand 1938
13 Fire blight of pear England 1940
14 Crown gall of apple/pear (Agrobacterium England 1940
tumefaciens)
15 Bunchy top of banana Srilanka 1940
16 Canker of apple Australia 1943
17 Wart of potato (Synchytrium endobioticum) Netherlands 1953
18 Golden nematode of potato Europe 1961
19 Sunflower downy mildew (Plasmopara holstedi) Australia 1985

Losses caused by introduced plant diseases: The entry of a single exotic insect or disease and
its establishment in the new environment continues to cause great, national loss. In certain cases
a country has to spend a few million rupees before success in controlling the introduced insect
pest or disease is achieved.

Table: Losses caused by introduced plant diseases

S. Disease Crop Host Introduced Losses caused

No. Country from
1 Bunchy top Banana India Sri Lanka Rs.4 crores
2 Wart Potato India Netherlands 2500acres infected
3 Canker Citrus U.S.A Japan $ 13 million; 19.5
million trees
destroyed

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4 Downy mildew Grapevine France U.S.A $ 50,000 million
5 Powdery Grapevine France U.S.A 80% in wine
mildew production

Plant quarantine methods

There are number of plant quarantine methods which are used separately or collectively
to prevent or retard the introduction and establishment of exotic pests and pathogens. The
components of plant quarantine activities are:

1. Complete embargoes
It involves absolute prohibition or exclusion of specified plants and plant products from a
country infected or infested with highly destructive pests or diseases that could be transmitted by
the plant or plant products under consideration and against which no effective plant quarantine
treatment can be applied or is not available for application.

2. Partial embargoes
Partial embargoes, applying when a pest or disease of quarantine importance to an importing
country is known to occur only in well defined area of the exporting country and an effectively
operating internal plant quarantine service exists that is able to contain the pest or disease within
this area.

3. Inspection and treatment at point of origin

It involves the inspection and treatment of a given commodity when it originates from a country
where pest/disease of quarantine importance to importing country is known to occur.

4. Inspection and certification at point of origin

It involves pre-shipment inspection by the importing country in cooperation with exporting
country and certification in accordance with quarantine requirements of importing country.

5. Inspection at the point of entry

It involves inspection of plant material immediately upon arrival at the prescribed port of entry
and if necessary subject to treatment before the same related.

6. Utilization of post entry plant quarantine facilities

It involves growing of introduced plant propagating material under isolated or confined
conditions.

Agencies involved in plant quarantine

The authority to implement the quarantine rules and regulations framed under DIP Act
rests basically with the Directorate of plant Protection, Quarantine & Storage, under the Ministry
of Agriculture. This organization handles bulk import and export of seed and planting material
for commerical purpose. Under this organization 9 seaports, 10 airports and 7 land frontiers are
functioning. These are the recognized ports for entries for import of plant and plant material.

The names and places of the ports and stations are as follows:
Seaports (9) Airports (10) Land Frontiers (7)
1. Bhavnagar - Gujarat 1. Amritsar - Punjab 1. Amritsar Railway Station -
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2. Calcutta - West Bengal 2. Calcutta - West Bengal Punjab
3. Chennai - Tamil Nadu 3. Chennai - Tamil Nadu 2. Attari Railway Station - Punjab
4. Cochin - Kerala 4. Hyderabad - Andhra 3. Attari-Wagah Border- Punjab
5. Mumbai - Maharashtra Pradesh 4. Bangaon Benapol Border - West
6. Nagapattinam - Tamil 5. Mumbai - Maharashtra Bengal
Nadu 6. New Delhi - New Delhi 5. Gede Road Railway Station -
7. Rameswaram - Tamil 7. Patna - Bihar West Bengal
Nadu 8. Tiruchirappalli - Tamil 6. Kalimpong - West Bengal
8. Tuticorin - Tamil Nadu Nadu 7. Sukhia Pokhri - West Bengal
9. Visakhapatnam - Andhra 9. Trivandrum - Kerala
Pradesh 10. Varanasi - Uttar Pradesh

Certification:
Phytosanitary or health certificate is a certificate which should accompany a plant or
plant material or seed which is to be moved from one place to another place. This certificate
indicates or certifies that the material under transit is free from pests or diseases.

Domestic Quarantine
Under the DIP Act, the Directorate of Plant Protection, Quarantine and storage has the
responsibility to take the necessary steps and regulate the inter-state movement of plants and
plant material in order to prevent the further spread of destructive insects and diseases that have
already entered the country. The sole object of enforcing domestic quarantine is to prevent the
spread of these diseases from infected to non-infected areas. Currently, domestic plant quarantine
exists in four diseases:

1. Bunchy top of banana: The export and the transport from the States of Assam, Kerala,
Orissa, West Bengal, Tamil Nadu to any other State of Banana plant or any other plant of the
genus Musa, including sucker, stem, leaf, flower, and any other part thereof which may be used
for propagation, or the materials of banana plant or any other plant of the genus Musa, which are
used for packing and wrapping, excluding the banana fruit is prohibited.

2. Banana mosaic: The export and transport from the States of Maharashtra and Gujarat of any
plant of Banana or any other plant of genus Musa including the sucker, stem flower and any
other part thereof, but excluding leaf and fruit thereof is prohibited.

3. Potato wart: The export to potato tubers from the State of West Bengal to any other State or
territory of India is prohibited.

4. Apple scab: The Directorate of Horticulture, Himachal Pradesh worked out a detailed scheme
for the eradication of scab, and prohibiting the export of planting material of apple outside the
State.

IV. BIOLOGICAL CONTROL

Definition: “Biological control of plant disease is a condition or practice whereby survival or

activity of a pathogen is reduced through the agency of any other living organism (except
human beings), with the result that there is reduction in incidence of the disease caused by
the pathogen (Garett, 1965).

12
According to Baker and Cook, 1974 “Biological control is the reduction of inoculum density
or disease producing activity of a pathogen or a parasite in its active or dormant state by one
or more organisms accomplished naturally or through manipulation of the environment of
host or antagonist by mass introduction of one or more antagonists”.
The four main mechanisms involved in the biocontrol are (i) the biological agent
(antagonist), may parasite the other organism, (ii) antagonist may secrete metabolites
(antibiotics) harmful to the pathogens (Antibiosis) (iii) antagonist may compete with the
pathogens for nutrients or space (Competition) and (iv) may cause death of the parasite by
producing enzymes (Lysis).
Parasitism and Lysis
The biocontrol against parasitizes the pathogen by coiling around the hyphae, e.g.,
Trichoderma viride; various bacteria and fungi secrete hydrolytic about the degradation of cell
wall of pathogens.
e.g. (i) Bacillus sp. causes hyphal lysis of Gaeumanornyces graminis
(ii) The chitnolytic enzymes of Serratia marcescens caused cell wall lysis of Scierotium
rolfsii.
(iii) Trichoderma sp. produces chitinases and β-1,3 glucanases which lyses the cell wall of
Rhizoctonia solani.
Antibiosis
The antibiotic compounds secreted by the biocontrol agent suppress the growth of the
pathogen. e.g. Phenazine-l-carboxylic acid produced by P fluorescens plays an important role in
suppressing the take all disease of wheat.
Competition
The biocontrol bacteria and fungi compete for food and essential elements with the
pathogen thereby displacing and suppressing the growth of pathogen.
e.g. (i) The competition for nutrients between Pythium aphanidermatum, P ultimum and bacteria
suppress the damping off disease in cucumbers.
(ii) Fluorescent siderophores (iron chelaters) such as pseudobactinis & pyoverdins produced
by P fluorescons chelates iron available in the soil, thereby depriving the pathogen of Its
Fe requirements.
Biocontrol agents for the management of plant pathogens
Biocontrol agent Pathogen/disease
1. Ampelomyces quisqualis Powdery mildew fungi
2. Darluca filum, Verticillium lecanii Rust fungi
3. Pichia gulliermondii Botrytis, Penicillium

13
 Biocontrol agent Nematode
1. Pasteuria penetrans (Bacteria) Juvenile parasite of root knot nematode
2. Paecilomyces lilacinus (Fungus) Egg parasite of Meloidogyne incognita
Important fungal biocontrol agents:
Most of the species of Trichoderma, viz., T. harzianum, T. viride, T. virens
(Gliocladium virens) are used as biocontrol agents against soil borne diseases, such as,
root rots, seedling rots, collar rots, damping off and wilts caused by the species of
Pythium, Fusarium, Rhizoctonia, Macrophomina, Sclerotium, Verticillium, etc.
Formulations of biocontrol agents available: T. viride (Ecofit, Bioderma in India),
G. virens (GlioGard in USA), T. harzianum (F-Stop in USA) and T. polysporum
(BINAB-T)
Important bacterial biocontrol agents:
1. Pseudomonas fluorescens (Dagger-G against damping off of cotton seedlings in USA)
2. Bacillus subtilis (Kodiak against damping off and soft rot in USA)
3. Agrobacterium radiobacter K-84 (Gallex or Galltrol against crown gall of stone fruits
caused by Agrobacterium tumefaciens)

V. HOST PLANT RESISTANCE

A physiological deviation from the normal functioning of the organism (i.e., the crop
plant) caused by pathogenic organisms is a disease and may be caused by fungi, bacteria or
viruses. The inherent ability of an organism (i.e., the crop plant) to resist or withstand the
pathogen is called resistance. Disease resistance commonly met with in the plant kingdom
relative in nature, total immunity being too rare. Its hereditary transmission from parent to off-
spring is essentially “Mendalian”, but often polygenic.
The earliest demonstration of the behaviour of “disease-resistance” as a character
transmissible from parent to off-spring in the “Mendelian” fashion was given by Biffen (1905) in
his work on yellow rust of wheat. Since then, intensive work has been done on this aspect which
has proved the value of applying genetical principles in developing disease-resistant varieties of
plants for effective control of diseases.
Resistant varieties can be the simplest, practical, effective and economical method of
plant disease control. The use of resistant varieties cannot only ensure protection against diseases
but also save the time, energy and money spent on other measures of control.
The resistance of a crop to a physiological race of the pathogen depends not only on the
genotype of the host for resistance, but also upon the genotype of the pathogen for virulence or
aggressiveness. Flor (1942) proposed the gene-for-gene hypothesis, according to which, for
every gene for resistance in the host, there is a corresponding gene for pathogenicity in the
pathogen.
It means that there are atleast two alleles at a locus controlling resistance/susceptibility in
the host (R-r) and two alleles at a corresponding locus in the pathogen (V-v) controlling
virulence / aggressiveness. Out of the four possible interactions between these alleles, only one
combination leads to the expression of resistance. The demonstration of gene-for-gene
relationship requires genetic studies of both the host and the pathogen.
14
Vertical resistance (VR) and horizontal resistance(HR)
Van der Plank (1960) has discussed the whole issue of disease resistance in a different
perspective. He calls the unstable and often complete type of resistance as vertical resistance and
the more stable but somewhat incomplete resistance as horizontal resistance. If resistance to
some races of a pathogen is more than to other races, it is called Vertical resistance. It is also
called Perpendicular resistance, Physiological resistance, seedling resistance, hypersensitivity,
race specific resistance or qualitative resistance. As it is conditioned by one or a few genes, it is
called major gene or monogenic of oligogenic resistance.
Resistance to more than one race of the pathogen or to many or all races of the pathogen
is called Horizontal Resistance. It is non-specific resistance governed by polygenes. It is
severally termed as non-specific, general, polygenic, minor gene, mature plant, adult,
quantitative resistance, partial or field resistance or tolerance. HR causes reduction in the number
and rate of sporulation of the pathogen on the host and slows down the infection rate. HR
includes tolerance slow development of disease, escape and exclusion mechanisms besides
hypersensitive reaction.

a. Disease escape
It is a prevention mechanism that causes the host to escape pathogenic infection. Early or
late maturity of the crop may prevent physical contact of the pathogen with the host. Mechanical
and anatomical barriers such as thick cuticle, waxy bloom on leaves and stem, stomatal
regulation prevent penetration of spores. Ergot, a fungal disease of inflorescence in cereals
caused by Claviceps purpurea does not affect varieties of wheat and barley in which the flowers
remain closed until pollination occurs. Erect leaves of barley avoid deposition of spores of
Erysiphe graminis tritici in contrast to prostrate leaves. Early maturing varieties of groundnut
escape early leaf spot infection (Cercospora arachidicola) and early varieties of wheat escape
rust and loose smut infection.
b. Disease endurance
The host after being infected by the pathogen tolerates the infection and suffers less
damage. It does not result in any substantial decrease in yield. This is brought about by influence
of external factors. It is a well-known phenomenon that plants fertilized with phosphatic and
potash manures are more tolerant to disease; this is the case in wheat against rust infection. Rice
crops fertilized by silicates are “resistant” to blast (Pyricularia oryzae) in Japan. Wheat crops
fertilized by potash and phosphatic manures are highly tolerant to mildew and rust infection. The
fertilizers act indirectly to arrest vegetative growth and promote early maturity, better straw and
strengthening tissues to protect the plant which form a bulwark against pathogenic invasion.
c. True resistance
It is the ability of the host plant to resist or withstand the attack of a pathogen. True
resistance is inheritable and much less subject to environmental influence. It is specific in
character. The basis of resistance may be morphological, functional, structural or protoplasmic.
Functional nature of resistance is determined by opening of the stomata, time of opening of
flowers and time of maturity, rate of cork formation and cambial activity.

15
True resistance, however, is of a specific character and is determined by the defence equipment
and activities of the plant itself against the parasitic invasion and is therefore not subject to any
appreciable modifications by external factors.
Methods of breeding for disease resistance
The methods of breeding varieties resistant to diseases do not differ greatly from those
adopted for other characters. The following methods are used:
1.Introduction

1. Selection

2. Hybridization followed by selection

3. Back cross method

4. Induced mutagenesis

5. Development of multilines

6. Tissue culture techniques

7. Genetic engineering

1. Introduction
It is a very simple and inexpensive method. Varieties resistant to a particular disease
elsewhere may be thoroughly tested in the regions in which they are proposed to be introduced.
Their yield performance and disease resistance should be confirmed by large scale cultivation. It
is possible that a variety resistant in one region need not be resistant in another region due to
variation in the physiological race of the pathogen or due to a much different agroclimatic
condition in the new location.
Introductions have served as a useful method of disease control. For example, from
Manila, a rice variety introduced in Karnataka from the Philippines, has tolerance to blast,
bacterial leaf blight and sheath blight. Early varieties of groundnut introduced from U.S.A. have
been resistant to leaf spot (Cercospora arachidicola).

2. Selection
This is better method than introduction and has more chances of success in obtaining
disease-resistant plants. The work of selection is carried out either in the naturally infected fields
16
under field conditions or under artificially inoculated conditions. The resistance in such
individuals will occur in nature by mutation. To ensure the resistant character of a plant, large
population of crop plant may be exposed to the attack of pathogen under artificial conditions and
the non-infected plants may be chosen. Sugandh of Bihar is a selection from Basmati rice of
Orissa tolerant to bacterial leaf blight.
3. Hybridization
When selection of resistant varieties is not feasible, resistant varieties may be evolved by
crossing the susceptible popular variety with resistant wild variety where in the resistant gene or
genes transferred into the genetic make up of susceptible variety. Very often the F1 from crosses
may be resistant but carry the other undesirable qualities of the resistant parent. The bad qualities
are removed by several back crossing of F1 with the susceptible parent may ultimately yield a
resistant progeny with good agronomic characteristics.
Under certain circumstances pedigree or bulk method of selection is followed to obtain a
resistant variety. In this method, the crosses are made till F2 population is got. Selections are
made in F2 generation for superior genetic traits including disease resistance. By continued
selfing, selections are made through F3 to F5 or F6 generations and the best variety is selected.
This method is suited for small grains and beans but unsuited to fruits and vegetables.
4. Back cross method
Back cross method is widely used to transfer disease resistance from wild species. Wild
species are rice sources of disease resistance. Interspecific hybridization is made to transfer the
gene or genes for resistance to the cultivated species. Resistance to grassy stunt virus from Oryza
nivara to O.sativa, late blight resistance from Solanum demissum to cultivated potato, rust
resistance from durum to aestivum wheat are some of the examples involving interspecific
hybridization. Depending upon the number of genes governing resistance and the nature of the
gene, whether dominant or recessive, the procedure varies. The number of back crosses to the
cultivated species may be five to six. Once the back cross progeny resemble the cultivated
parent, then they are selfed and segregating progeny screened for disease resistance.
5. Induced mutagenesis
While following mutation breeding for disease resistance, a large number of mutation
progeny should be produced and screened under artificial epiphytotic condition to select resistant
plants. MCU10 cotton, a resistant variety to bacterial blight was evolved in Tamil Nadu by
subjecting seeds of a susceptible variety CO4 to gamma rays followed by rigorous screening and
selection 6. Development of multilines The concept of multilines was first suggested by
Jensen(1952) and developed by Borlaug (1959) for evolving multiline varieties to resist stem rust
in wheat. A multiline variety is a composite of genetically similar lines, except that each line
possesses a different gene for resistance to the pathogen.

Lines that are genetically similar, except for one gene, are called isoline. It is assumed
that gene for resistance in each isoline contributes resistance to a separate physiological race or
group of races. Genes for disease resistance are transferred by backcrossing from donor varieties
to a common disease susceptible, but agronomically superior, recurrent parent. Isolines are
generated differing only in the gene for disease resistance. The isolines are composited to
synthesize a multiline variety. The isolines are maintained for resynthesizing the multiline
17
whenever needed. A multiline variety is composed of a mixture of resistant and susceptible
genotypes and provides a buffering effect against rapid development of disease. It will provide
resistance or tolerance to a broad spectrum of races of a pathogen. If new races of the pathogen
are identified at a later stage, additional isolines resistant to the newly arisen races may be
constituted and incorporated. Kalyan sona and Sonalika-based multilines of wheat resistant to
different races of rust have been developed in India.
7. Tissue culture technique
Tissue culture techniques to produce somaclonal variation for disease are developed in
different crops. Somaclonal variations for disease resistance are reported in Zea mays for
Drechslera maydis race T-toxin resistance, in Brassica napus for resistance/tolerance to Phoma
lingam, early and late blight resistance in potato, Pseudomonas and Alternaria resistance in
tobacco, besides smut and rust disease resistance in sugarcane.
8. Genetic Engineering is the technology by which a particular gene is isolated from one
organism and inserted into the genome of another organism and made to express at the right
time.

VI. CHEMICAL CONTROL

CHEMICAL CONTROL OF PLANT DISEASES:
STUDY OF DIFFERENT FUNGICIDES & ANTIBIOTICS
Use of chemicals in plant diseases management is included in the principles of
protection or therapy.
 Protection
The prevention of the pathogen from entering into the host or checking the further
development in already infected plants by the application of chemicals is called
protection and the chemicals used are called protectants.
 Therapy
Therapy means cure the disease, in which fungicide is applied after the pathogen is
in contact with the host. Chemicals used are called therapeutants.
 Fungicides
The word fungicide originated from two Latin words, viz., “fungus” and “caedo”.
The word “caedo” means to kill. Thus, these are biocidal chemical compounds used to
kill fungi or fungal spores.
 Fungistat
Some chemicals which do not kill fungi, but simply inhibit the fungus growth
temporarily which is known as fungistat and the phenomenon of temporarily inhibiting
the fungal growth is termed as Fungistatics.
 Antisporulant
The chemical which inhibits spore production without affecting vegetative growth
of the fungus.
Characteristics of a good (ideal) fungicide

18
 Low phytotoxicity: Ideal fungicide should not be toxic to the plants.
 It should have long shelf life.
 It should be less toxic to human being and cattle etc. It should not be toxic to
earthworms and beneficial soil microorganisms.
 It should have high toxicity to a wide range of fungi
 It should not cause accumulation of toxic chemicals in soil or in plants or in plant
products.
 It should combine with important or commonly used insecticides or acaricides
without any deleterious effects.
 It should be cheap (economical) and easily available in the market and easily
transportable.
 It should be available in different formulations.
 It should easily spread on the host surface when applied.
 It should not cause environmental pollution.

CLASSIFICATION OF FUNGICIDE
1. BASED ON MODE OF ACTION
(I) Protectant: Fungicide which protects a plant from a pathogen if it is applied prior to
infection. They are prophylactic in their behaviour. Contact fungicides
which kill the pathogen present on the host surface when it comes in
contact with the host are called protectants. These are applied to seeds,
plant surfaces or soil. These are non-systemic in action (i.e. they cannot
penetrate plant tissues). e.g. Sulphur, Zineb.
(II) Therapeutant: Fungicide which eradicates a fungus after it has caused infection
thereby curing the plant is called therapeutant. Usually
chemotherapeutants are systemic and eradicates deep seated infection.
e.g. Carboxin, Oxycarboxin, Aureofungin
(III) Eradicant: A chemical substance that destroys (eradicate) pathogen after its
establishment in the host plant is known as eradicant. It eradicates the
dormant or active pathogen from the host. It also acts as protectant. They
can remain on/in the host for some time. e.g. Organomercurials, Lime
sulphur, Dodine.
2. BASED ON GENERAL USE
1 Seed protectants Organomercurials, Captan, Thiram, Carbendazim,
19
 Carboxin
2 Soil fungicides Bordeaux Mixture, Copper Oxychloride, Vapam,
(Pre-plant) Chloropicrin, Formaldehyde
3 Soil fungicides (when Bordeaux Mixture, Copper Oxychloride, Thiram,
plants are in field) Captan
4 Foliage and blossom Bordeaux Mixture, Copper Oxychloride, Ferbam,
protectants Zineb, Mancozeb, Captan, Carbendazim,
Chlorothalonil
5 Fruit protectants Maneb Mancozeb, Captan, Carbendazim,
Thiabendazole
6 Tree wound dresser Bordeaux Paste, Chaubattia Paste
7 Antibiotics Streptomycin, Streptocycline, Griseofulvin

3. BASED ON CHEMICAL COMPOSITION

(A) Sulphur Fungicides
Sulphur is probably the oldest chemical used in plant disease management for the
control of powdery mildews. Robertson first recommended to use sulfur as fungicide for
control of powdery mildew of peach.
(I) Inorganic Sulphur: Lime Sulphur and Elemental Sulphur fungicides.
(II) Organic Sulphur: It also called as carbamate fungicides. e.g. Zineb, Thiram.
(I) Inorganic Sulphur
Common name Trade name Disease
managed
1. Lime sulphur It is manually prepared by mixing rock lime Powdery
and sulphur along with water mildews of
2. Sulphur dust Kolo dust, Mico- 999 various crops
3. Wettable sulphur Sulfex, Thiovit, Cosan

(II) Organic Sulphur Compounds

Organic sulphur compounds are derived from dithiocarbamic acid and are widely
used as spray fungicides. In 1931, Tisdale and Williams were the first to describe the
fungicidal nature of Dithiocarbamates.
Dithiocarbamates can be categorized into two groups, viz., dialkyl
dithiocarbamates and monoalkyl dithiocarbamates.
Common name Trade name Disease managed
1. Ziram Ziride Anthracnose of pulses, tomato, beans.

2. Thiram Thiram, Thiride Soil borne diseases

20
 3. Zineb Dithane Z-78, Chilli die-back and fruit rot, early
blight of potato
5. Mancozeb Dithane M-45, Early and late blight of potato and
Indofil M-45 tomato, rust diseases of field and fruit
crops

(B) Copper Fungicides: Copper fungicides can be classified as preparatory and

proprietary copper compounds.
PREPARATORY COPPER FUNGICIDES
Common name Chemical Diseases managed
composition
Copper Sulphate Preparation
1. Bordeaux Mixture Copper Sulphate + Downy mildew of grapes,
(PMA Millardet) Hydrated Lime + Citrus canker etc.
Water
2. Bordeaux Paste Copper Sulphate + It is a wound dressing
Hydrated Lime + fungicide and applied to the
Water pruned parts of the plant.
Citrus gummosis, Stem
bleeding of coconut

3. Burgundy Mixture Copper Sulphate + Fungal diseases of trees and

(Mason) Sodium Carbonate + fruit plant
Water
4. Cheshunt Compound Copper Sulphate + It is used for soil drenching
(Bewley) Ammonium Carbonate only. Damping-off diseases of
solanaceous crops
Copper Carbonate Preparation
5.Chaubattia paste Copper Carbonate + Pink disease of citrus, stem
(Singh) Red Lead + Lanolin canker and collar rot of apple
Or Linseed Oil and pears

PROPRIETARY COPPER FUNGICIDES or FIXED or INSOLUBLE COPPER

FUNGICIDES
In the fixed or insoluble copper compounds, the copper ion is less soluble than in
Bordeaux mixture. So, these are less phytotoxic than Bordeaux mixture but are effective as
fungicides.
Common name Trade name Disease managed
1. Copper Oxychloride Blitox-50, Anthracnose of Grapevine, Tikka
21
 Blue copper- 50 leaf spot of groundnut, Citrus
Canker
2. Cuprous Oxide Fungimar, Perenox -“-

3. Copper Hydroxide Kocide Blister blight of tea, False smut of

rice, Tikka leaf spot of groundnut

(C) Mercurial Fungicides

Mercury compounds have been in use for a long time for treating seeds, rhizomes,
corms, bulbs etc. of vegetables and flowering plants for the control of seed-borne
diseases. It have fungicidal and bactericidal activity. They are highly toxic towards
animals and human beings and at times even phytotoxic. Because of their extreme
toxicity the usage on foliage is limited. Mercury fungicides are banned in almost all
countries including India because of their toxic nature and persistence to get into the food chain.
Common name Trade name Disease
managed
I. Inorganic Mercury Seed Borne
1. Mercuric chloride Merfusan, Mersil Disease
2. Mercurous chloride Cyclosan, M-C Turf
II. Organomercurials Agallol, Aretan,
Methoxy ethyl mercury Chloride (MEMC) Emisan
(D) Heterocyclic Nitrogenous Compounds
Captan, folpet and captafol belong to dicarboximides and are known as
phthalamide fungicides. First heterocyclic nitrogenous compounds Captan was
discovered by Kittleson.
Common name Trade name Disease managed

1.Captan Captan 50W, Captan 75 W Seed borne disease

(Kittleson’s killer)
2.Captafol Difosan, Difolaton
3. Iprodione Rovral, Glycophene Diseases caused by Alternaria,
Sclerotinia, Helminthosporium

(E) Benzene Fungicides

Common name Trade name Disease managed

1.Chlorothalonil Bravo, Kavach Foliar Diseases

2. Dinocap Karathane Powdery mildews diseases in many crops

22
(F) Organo Phosphorus Fungicides: Ediphenphos
(G) Quinone Fungicides: Chloranil, Dichlone etc.
(H) Organo Tin Compounds: Du-ter, Brestanol etc.
(I) Systemic Fungicides
These are fungi toxic compounds which when applied on different parts of the
plant are absorbed by the plant tissues and then translocated upwards, downwards and
both ways and act on the pathogen either directly or through its metabolic products and
control plant diseases away from the point of application.
The systemic fungicides (Oxathiin) was first discovered by Von Schelming
and Marshall Kulka in 1966. On the basis of chemical nature these fungicides are
classified as follows.
Common name Trade name Disease managed
Acylalanines
1. Metalaxyl Ridomil, Apron It is highly effective against
Pythium, Phytophthora and many
downy mildew fungi.
Aromatic Hydrocarbons
1. Chloroneb Demosan Seedling diseases of cotton, peanut
and peas.
Benzimidazoles Compound
1. Carbendazim Bavistin Many Foliar and Soil borne
diseases
2. Benomyl Benlate Highly effective against diseases
caused by the species of
Rhizoctonia, Theilaviopsis and
Cephalosporium
3.Thiabendazole Mertect Blue and green molds of citrus,
loose smut of wheat, Tikka leaf
spot of groundnut
Oxathins or Carboximides
1. Carboxin Vitavax Seed bone diseases
2.Oxycarboxin Plantavax Highly effective against rust
diseases.
Morpholines
1. Tridemorph Calixin Powdery mildew, Rusts
(Now Banned in India)
Organophosphates

23
1. Iprobenphos Kitazin Rice blast, stem rot and sheath
blight of rice
2. Ediphenphos Hinosan Rice blast, stem rot and sheath
blight of rice
Alkyl Phosphonates
1. Fosetyl-Al or Aliette Specific against Oomycetes fungi
Aluminium Tris
Thiophanates
1.Thiophanate methyl Topsin M Blast and sheath blight of rice,
sigatoka leaf spot of banana
Triazoles
1. Hexaconazole Contaf Rust, Powdery Mildew and other
2. Propiconazole Tilt foliar diseases
3. Difenconazole Score
4. Tebuconazole Folicure
5. Flusilazole Nustar, Cursor
6. Myclobutanil Systhane
Strobilurins (Isolated from wood rotting mushroom fungi, (Strobilurus tenacellus)
1. Azoxystrobin Amistar, Quadris Broad spectrum fungicide
2. Kresoxim methyl Ergon, Discus Commonly used for control of
ornamental diseases
3.Pyraclostrobin Headline Early blight

(II) Based on Chemical Composition

(A) Sulphur fungicide
 Organic Sulphur: Zineb, Mancozeb, Ziram, Thiram etc.
 Inorganic Sulphur: Elemental Sulphur, Sulphur Dust, Lime Sulphur etc.
(B) Copper fungicide
 Copper Sulphate Preparations: Bordeaux mixture, Bordeaux paste, Burgundy
mixture, Cheshunt compound, Fytolan, Copper oxychloride etc.
 Copper Carbonate Preparation: Chaubbatia paste etc.
(C) Mercury fungicide
 Inorganic Mercury: Mercuric chloride, Mercurous chloride etc.
 Organomercurials: Methoxy ethyl mercury chloride, Ethyl Mercury Chloride etc.
(D) Quinone Fungicides: Chloranil, Dichlone etc.
(E) Heterocyclic Nitrogenous Compound: Captan, Captafol etc.
(F) Organo Phosphorus Fungicides: Ediphenphos
24
(G) Benzene Fungicides: Chlorothalonil, Dinocap, Penta chloro nitrobenzene etc.
(H) Organo Tin Compounds: Du-ter, Brestanol etc.
(I) Systemic Fungicides
 Oxathilin and Related Compounds: Carboxin, Oxycarboxin etc.
 Benzimidazoles compound: Benomil, Thiabendazole, Carbendazim etc.
 Thiophanates: Thiophanate methyl
 Morpholines: Tridemorph
 Sterol Biosynthesis Inhibitor Fungicides: Propiconazole, Triadimefon etc.
 Acylalanines or Acylanilides: Metalaxyl, Cyprofuram etc.
 Strobilurins Fungicides: Azoxystobin, Picoxystrobin etc.
 Organic Phosphate: Fosetyl- Al, Kitazin etc.
 Miscellaneous Systemic Fungicides: Ethazole, Chloroneb etc.
(J) Antibiotics
 Antibacterial Antibiotics: Streptomycin, Tetracyclines etc.
 Antifungal Antibiotics: Aureofungin, Griseofulvin, Blasticidin, Kasugamycin etc.
(K) Fumigant: Formalin 40%, Chloropicrin, Ethylene dibromide etc.

FUNGICIDES AND THEIR MODE OF ACTION

Group Member Mode of Action Pathogen
Systemic Fungicides
Carboximides Carboxin, Puccinia,
Oxycarboxin Ustilago, Tilletia,
Mitochondrial
Dinitrophenols Dinocap Powdery mildews
Electron Transport
Strobilurins Azoxystrobin All the pathogens
Inhibitors
Picoxystrobin group
Kresoxim-Methyl
Phenylamides Metalaxyl Nucleic acid Oomycetes
biosynthesis Phytophthora,
inhibitors Pythium,
Benzimidazoles Carbendazim, Mitosis and cell All fungal
Benomyl, division inhibitors pathogens except
Thiabendazole Oomycetes
25
 Thiophanate-
Methayl
Dicarboximides Iprodione Botrytis, Septoria,
Lipid and
Alternaria
membrane
Organophosphates Edifenphos, Pyricularia,
synthesis inhibitors
Iprobenfos Rhizoctonia
Triazoles Hexaconazole, Sterol biosynthesis All pathogens
Propiconazole inhibitors except Oomycetes
Morphilines Tridemorph
Non-Systemic (Contact) Fungicides
Copper fungicides Copper Multisite contact Oomycetes,
inhibitors Septoria,
(Disrupt function of Fusarium
enzymes, energy
transport systems,
integrity of
membranes)
Inorganic Sulphur Elemental sulphur Multisite contact Powdery mildews
inhibitors
(Inhibit electron
movement and
interferes with
cellular respiration)
Dithiocarbamate Mancozeb, Thiram Multisite contact Leaf spots, blights
inhibitors
(Reacts with
protein)
Heterocyclic Captan Multisite contact Oomycetes,
nitrogenous inhibitors Alternaria,
compounds (Inhibits enzymes Cercospora,
and interferes with Rhizoctonia
decarboxylation
process and citrate
synthesis)
Phosphonate Fosetyl- Al Multisite contact Phythium
inhibitors Phytophthora
(Inhibits oxidative Plasmophora
phosphorylation)
Difference between Systemic fungicides and Non-systemic fungicides
Systemic fungicides Non-systemic fungicides

26
1 Any compound capable of being Do not get absorbed and translocated
translocated after penetrating the plant & into the plant.
reaches to the point of infection.
2 Movement of fungicide may be No movement of fungicides (contact in
apoplastic (Upward movement) or nature)
symplastic (Downward movement)
3 Single site inhibitor Multisite inhibitor
4 Long persistence Short persistence
5 More chances of development of Minimum chances of development of
fungicidal resistance fungicidal resistance
6 Used in low concentration i.e. 0.025 to Used in higher concentration i.e. 0.2 to
0.05% 0.3%
7 e.g. Carbendazim, Hexaconazole etc. e.g. Thiram, Captan, Mancozeb etc.

Some Examples of Ready-Mix (Combination Fungicides)

Sr. Chemical name of Disease Managed Trade name
No. fungicides
1. Carbendazim 12% + Rust & Leaf Spot of groundnut SAAF, Sixer
Mancozeb 63% WP
2. Azoxystrobin 11% + Fruit rot, Powdery mildew, Die back Custodia
Tebuconazole 18.3% SC
3. Carboxin 37.5% + Seed borne diseases Vitavax
Thiram 37.5 WS% Power
4. Tebuconazole 50% + Foliar Diseases Nativo
Trifloxystrobin 25% WG
5. Metalaxyl 8% + Downy mildew or disease caused by Ridomil MZ
Mancozeb 64% WP Oomycota fungi
Antibiotics in Plant Disease Management
 Antibiotics
Antibiotic is defined as a chemical substance produced by one micro-organism
which is low concentration can inhibit or even kill other micro-organism. They have
systemic action in plants moving in both directions. They act as eradicant and protectants
as well. Antibiotics are antibacterial and antifungal in nature. Some examples of
antibiotics have been mentioned below:
I. Antibacterial Antibiotics
1. Streptomycin
Streptomycin is an antibacterial, antibiotic produced by Streptomyces griseus. This
was the first broad spectrum antibiotics discovered by SA Waksman and A Schatz.

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Streptomycin are streptomycin sulphate is sold as Agrimycin,-100, Streptomycin
sulphate, Plantomycin etc. This group of antibiotics act against a broad range of bacterial
pathogens causing blights, wilt, rots diseases.
The primary mechanism of action of streptomycin is binding irreversibly to
bacterial ribosomes and thereby inhibiting protein synthesis. At high concentrations,
streptomycin can be phytotoxic to plants; thus it is applied to the surface of plants and not
injected.
2. Tetracyclines
Antibiotics belonging to this group are produced by many species of Streptomyces.
All these antibiotics are bacteriostatic, bactericidal and mycoplasmastatic. These are very
effective against seed-borne bacteria. This group of antibiotic is very effective in
managing MLO (Phytoplasma) diseases of a wide range of crops.
Tetracyclines inhibit protein synthesis by binding reversibly to bacterial
ribosomes. Tetracycline derivatives are the only antibiotics that are registered for internal
use in plants. They are injected into the trunks of palm and elm trees to treat lethal
yellows diseases caused by phytoplasmas.
II. Antifungal Antibiotics
1. Aureofungin
It is fungal antibiotic produced in sub-merged culture of Streptoverticillium
cinnamomeum var. terricola. It is used for control of citrus gummosis, powdery mildew
of apple, apple scab etc.
2. Griseofulvin
This antifungal antibiotic was first discovered to be produced by Penicillium
griseofulvum and now by several species of Penicillium, viz., P.patulum, P.nigricans.
It is commercially available as Griseofulvin, Fulvicin and Grisovin. It is highly toxic to
powdery mildew of beans and roses, downy mildew of cucumber.

3. Cycloheximide
It is obtained as a by-product in streptomycin manufacture. It is produced by
Streptomyces griseus and S. nouresi. It is commercially available as Actidione and
Actispray. It is active against a wide range of fungi and yeast. Its use is limited because it
is extremely phototoxic. It is also used against leaf spot, leaf blast of paddy etc.
4. Blasticdin
It is a product of Streptomyces griseochromogenes and specifically used against
blast disease of rice. It is commercially sold as Bla-s.
5. Kasugamycin

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 It is obtained from Streptomyces kasugaensis. It is also very specific antibiotic
against rice blast disease. It is commercially available as Kasumin.
6. Thiolution
It is produced by Streptomyces albus and effectively used to control late blight of
potato and downy mildew of cruciferous vegetables.
7. Endomycin
It is a product of Streptomyces endus and effectively used against leaf rust of
wheat and fruit rot of strawberry (Botrytis cinerea).
8. Bulbiformin
It is produced by a bacterium, Bacillus subtills and is very effectively used against
wilt diseases, particularly red gram wilt.
9. Nystatin
It is also produced by Streptomyces noursei. It is successfully used against
anthracnose disease of banana and beans. It is commercially marketed as Mycostain and
Fungicidin.
10. Eurocidin
It is an antibiotic produced by Streptomyces anandii. It is effectively used against
diseases caused by several species of Colletotrichum and Helminthosporium.

FUNGICIDE FORMULATION
Fungicides formulation is a process by which the fungicides is put into a form
which can be easily produced, stored, transported and applied by practical methods in
order to achieve a safe, convenient, economic and effective methods of disease control. It
is a mixture of the active and inert ingredients in the fungicide. Pure chemicals are rarely
used to control pathogens. They are usually combined with other inert materials that
improve the physical and chemical properties of the product. Commercial fungicides are
formulated in various ways like as;

1. Liquid Formulation
 Emulsifiable concentrates (EC): They contain a liquid active ingredient, one or
more petroleum-based solvents and an agent that allows the product to be mixed with
water to form an emulsion. e.g. Tridemorph 80% EC, Dinocap 48% EC,
Hexaconazole 5% EC.
 Solutions: Solutions are formulations in which active ingredients readily dissolve
when mixed with a solvent such as water or a petroleum-based solvent. Solutions can
be used in any type of sprayer.

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 Suspension or Slurries: These are formulations in which a dry form of the active
ingredients is mixed with liquid along with an inert ingredient to form a suspension.
These are generally used as a seed dresser in different seed processing companies.
2. Dry Formulations
 Wettable powder: They are dry, finely ground formulations that look like dusts.
They are usually mixed with water for application as a spray. e.g. Mancozeb 75%
WP, Copper oxychloride 50% WP, Carbendazim 50% WP, Chlorothalonil 75% WP.
 Dust: Ready to use formulations which usually contain 1-10% of active ingredient
combined with a fine, dry inert carrier made from talc, chalk, clay, or volcanic ash.
e.g. Sulphur dust.
 Granules (Pellets): Granules formulations are similar to dust formulations, except
granular particles are larger and heavier. The granules contain normally 3-10% of the
active ingredients. e.g. Carbofuran 3G, Phorate 10G.

Different Types of Pesticides Formulations

C = Concentrate L = Liquid
CS: Capsule suspension LC = Liquid concentrate
DP: Dustable Powder LV = Low volatile
DS: Powder for Dry seed Treatment P = Pellets
D = Dust PA: Paste
DC: Dispersible concentrate PS = Seed coated with Pesticides
EG: Emulsifiable Granules RTU = Ready to use
EP: Emulsifiable Powder S = Solution
ES: Emulsion for seed Treatment SC: Suspension Concentrate
WP = Wettable powder SE: Suspension Emulsion
WDG = Water-dispersible granules SL: Soluble concentrate
WSP = Water-soluble powder SP = Soluble powder
WSC = Water-soluble concentrate WSL = Water-soluble liquid

METHODS OF FUNGICIDE APPLICATION

I. Foliar Application
 Spraying
Many inorganic or organic fungicides including systemic/ non-systemic and
antibiotic are generally applied by spraying either with high volumes or with low
volumes sprayers. The different equipments used for spray application are foot-operated
sprayer, rocking sprayer, knapsack sprayer, motorized knapsack sprayer (power sprayer),
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tractor mounted sprayer, mist blower and aircraft or helicopter (aerial spray). The main
objective of spraying is to provide protective covering over surface before arrival of the
pathogen.
 Dusting
In soluble or non suspended materials are used for dusting on foliage. Dust
formulations are dusted with the help of dusters like hand duster, bellows duster, rotary
hand duster etc; e.g. Sulphur duster for Powdery mildew of coriander.
II. Seed Treatment
Seed tubers, bulb and other planting materials are given chemical treatment for
eradication of pathogen present on them and for preventing in soil after planting.
Sometimes for seed borne disease, seed treatment is the only method of control. e.g.
cover Smut of barley and grain smut of bajra.
(A) Dry Seed Treatment: Dressing of seed with dry fungicide. In this method, the
fungicide adheres in a fine form on the surface of the seeds. A calculated quantity of
fungicide is applied and mixed with seed either manually with hands or using machinery
specially designed for the purpose. e.g. Captan, Thiram, Sulphur dust @ 2-3g /kg seed. It
is very effective against externally seed borne pathogen causing disease.
(B) Wet Seed Treatment: This method involves preparing fungicide suspension in water
and dipping the seeds or seedlings or propagative materials in it for a specified time. It is
very effective against internally seed borne disease. Seed treatment is given by various
compounds e.g. Organomercurial PCNB, Streptomycin, Thiram, Captan, carbendazin etc.
(C) Slurry Treatment (Seed Pelleting): In this method, chemical is applied in the form
of a thin paste (active material is dissolved in small quantity of water) to the seed. The
required quantity of the fungicide slurry is mixed with the specified quantity of the seed
so that during the process of treatment slurry get deposited on the surface of seeds in the
form of a thin paste which later dries up. Seed processing units have usually slurry
treaters, which mix the fungicide slurry with specified quantity of seeds before the seed
lot is bagged.
III. Soil Treatment
Soil treatment is given to reduce the amount of inoculum present in soil. This
treatment is effective for soil borne pathogens. The fungicides are applied in soil in
different forms by different methods:

(A) Soil Drenching

A suspension of chemical before sowing or after emergence of seedling is applied
with the help of sprinkler or water can in a unit area. This method is mostly employed for
the control of damping off disease, root rot or any soil borne pathogen at ground level
e.g. Bordeaux mixture (BM) for foot rot of Papaya. Carbendazim for control of wilt in
different cultivated crops.
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(B) Broadcasting
In this method, fungicide is to be applied in a same way as in case of fertilizer
application. In this methods, generally granular fungicides is utilised which is
broadcasted nearer to the plant. By this method, more quantity of fungicide is required
and hence it is not commonly employed. e.g. sulphur is applied at the rate of 25kg in
Bajra and Sorghum.

(C) Furrow Method

Whenever the crop is planted in rows this method is employed. A required
quantity of chemical to be applied in opened furrow in soil and mixed. Sow the seeds and
irrigate the field. e. g. Carbofuran, Phorate

(D) Soil Fumigation

Application of certain chemicals to the soil can control fungi and nematodes. Such
material usually produce a gas that distributes itself through the soil. This method is
usually restricted to small areas and high value crops. Volatile toxicants (fumigants) such
as methyl bromide, chloropicrin, formaldehyde and vapam are the best chemical
sterilants for soil to kill fungi and nematodes as they penetrate the soil efficiently.
Fumigations are normally done in nursery areas and in glass houses.
(E) Chemigation
The fungicides are directly mixed in the irrigation water. It is normally practiced
when sprinkler or drip irrigation system is followed in a field or garden.

IV. Paste and Paint

In fruit orchard, the wound created during pruning and trimming of trees and often
served as opening for entry of the pathogen. The fungicide paste or paints are used as
protective layers. The paste is prepared with chemical like CuSO 4 + Lime, CuSO4 +
CaCO3 etc. The residual effect is long lasting enough to permit natural healing of cut
surface e.g. Control of Margo Dieback, Citrus Gummosis.
Difference between Spraying of fungicides and Dusting of fungicides
Spraying of fungicides Dusting of fungicides
1 Formulation used in liquid form either Formulation is used in powder form
wettable powder (WP) or EC
formulation
2 Can be used in high wind velocity Not used in high wind velocity
3 More area covered Less area covered
4 Material needs preparation Materials is ready to use

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5 More effective Less effective
6 Particle size biger Particle size smaller
7 Sprayer is used Duster is used
8 Water is required Water not required
9 e.g. Mancozeb, Carbendazim e.g. Sulphur dust
Auxiliary Spray Materials (ADJUVANTS)
(1) Wetting agents: They facilitate contact between spray and sprayed surface. They
reduce the surface tension of the spray liquids and improve the surface of contact and
help to spread. e.g. Alcohol, Ester of Fatty acid.
(2) Spreaders: They improve the contact between spray materials and plant surface.
They help in the good coverage of the fungicide. e.g., Soap, Saponins, Mineral Oils,
Glyceride Oil, Terpene Oil etc.
(3) Stickers: They are materials added to increase tenacity e.g. Fish Oil, Milk, Gelatin.
(4) Deflocculating agents: Materials added to keep particles away from each other to
prevent flocculation to ensure dispersion and retard sedimentation eg. Gum, Gelatin and
Milk Products.
(5) Safeners: A chemical which reduces the phytotoxicity of another chemical is called
safener. Lime is added to copper sulphate in the preparation of Bordeaux mixture as a
safener. Glyceride oils are also used as safener.

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